Recently, with the rapid development of space technology, deep space exploration has become a space activity which people all over the word are striving to implement. During the process of deep space exploration, the main task of people is to seek for life. As a fixed star that is the closed to the earth and has the possibility of signs of life, Mars also becomes the first station of people's journey for exploring the deep space. In view of the tasks that have been performed by people on Mars, the demand for landing precision will become higher and higher in the future Mars exploration. However, in consideration of the distance from Mars to the earth and all the unpredictable uncertainty factors on Mars, improvement of Mars landing precision faces with a huge challenge. An in-flight guidance system in a Mars lander may perform guidance law calculation, and thus plays an important role in adjusting the guidance precision of the lander. Except the Curiosity Explorer, all current Mars landing tasks adopt a guidance-free mode, and therefore landing precision cannot be ensured. The guidance method used by the Curiosity Explorer is a tack guidance method based on reference ground track, and is very weak in adaptability. In the case that Mars atmosphere density is highly indeterminate, the lander entering point has a deviation and the navigation measurement precision can hardly be ensured, it is difficult to improve the landing precision of the lander. A traditional prediction-correction guidance method can realize on-line generation of a guidance law, and thus can efficiently improve the adaptability of the lander. However, the prediction-correction guidance method has an extremely high requirement for the model precision of the lander, and the harsh environment of Mars has a significant impact on the precision of the guidance method. Related research has been conducted on the guidance method in the Mars atmosphere-entering phase in China. A method for precise control in a lander-entering phase based on feedforward compensation was provided in patent No. 201510303486.0. But there is a problem: in the current Mars landing task plan, the demand for surround-land-patrol integration requires the lander to implement on-line guidance law design and arrive the predetermined parachute-opening point without depending on the reference ground track, thereby ensuring the landing precision, and this method is relatively weak in autonomy.
Accordingly, there is a need for a method for anti-disturbance composite on-line guidance in the atmosphere-entering phase of a Mars lander that is able to efficiently implement on-line guidance, estimate and compensate Mars atmosphere uncertainty disturbances.